bheemamahesh ..i do want to ask u one thing..have u ever made an image of your XP system?? I m asking this becoz "if u want to keep fedora and XP both in working condition then u can copy the system image to C:\(or root directory) mounted folder so that windows may come back again in working condition...
IF you had not made any image then dnt worry..try finding out "rescue disk" for Kaspersky or Bid defender. Rescue disks are live disks. It will surely bypass the GRUB. Once bypassed, scan your windows partition in search for viruses and after the process ends try booting up ur XP.
You are asking about GRUB? It is difficult to explain you in simple language. But i m giving u a link which is very useful:-http://www.dedoimedo.com/computers/grub.html

u can do one thing which i did once when i faced the same problem:-
1) boot with ur fedora DVD
2) format the fedora partition just to give it the assurance that u r going to do the fresh installation.
3) after formatting the partition to ext3 proceed to the new installation.
4)once the installation starts take out ur DVD quickly , reboot and quickly insert the XP CD.

voilla u r done...but u will lose the fedora...

ThanX 4 Replying 2 my Silly Queries

i have tried the above method but
after these steps
--> after formatting the partition to ext3 proceed to the new installation.
-->once installation starts take out ur DVD quickly ,reboot and quickly insert XP CD.
same problem raises for me

if i start the system normally without any disk it shows like dos with prompt Grub as follows
grub>